1. Field of the Invention
Flavobacterium columnare is an aquatic bacterium that is highly infectious in both warm and cold water species of fish. In the channel catfish (Ictalurus punctatus), it is the causative agent of columnaris disease. Flavobacterium columnare is a Gram-negative, rod shaped pathogen that has been isolated from channel catfish in areas of the southeastern United States where this species is cultured. The disease also affects sport fish such as perch, walleye, pike, centrachids (bass and sunfish), aquarium fish and baitfish. Medicated feed with several chemotherapeutics has been suggested to control columnaris disease, but these have limited effectiveness and are not approved for use on food fish. Presently, most producers have discontinued use of medicated feeds. Estimated savings to the aquaculture industry in addition to reducing antibiotic and chemical use in aquatic production systems will result from use of this vaccine.
This invention relates to a novel vaccine against columnaris which functions by reducing the bacteria's ability to adhere to the fish.
2. Description of the Prior Art
It has been estimated that columnaris is the second leading cause of mortality in pond raised catfish in the southeastern United States. Based on the success of disease control by immunization with killed bacteria (i.e., bacterins) in salmonids, experimental bacterins have been developed and tested against F. columnare. However, no vaccine is currently available that functions by reduction of adhesion of the bacteria to the catfish and other warm water fish. This type of vaccination is not practiced in the catfish industry against F. columnare, presumably because the bacterin preparation process of inactivation (i.e., formalin treatment) destroys the antigen [Bader et al., Comparison of whole-cell antigens of pressure and formalin-killed Flexibacter columnaris from channel catfish (Ictalurus punctatus), American Journal of Veterinary Research 58:985–988, 1998]. The patent of Wolf-Watz et al., U.S. Pat. No. 5,284,653, presents a whole list of bacteria one of which is Flexibacter columnaris (now referred to as F. columnare in industry) which has the potential to be modified to produce a vaccine. However, no data are presented on F. columnare vaccines, only on modified mutant vaccines of Vibrio anguillarum and no suggestion is made to altering adhesion, a key virulence factor in F. columnare infection. Bernadet (Immunization with bacterial antigens: Flavobacterium and Flexibacter infections, Fish Vaccinology: Developments in Biological Standardization, Volume 90, pp. 335–340, 1997); Karger (Switzerland, Basel) reviews the limited knowledge available on F. columnare and vaccination against this important disease. Work suggests that rainbow trout (Oncorhynchus mykiss) which survive infection with F. columnare are immune to subsequent disease.